| Noun | 1. | order Psilotales - lower vascular plants having dichotomously branched sporophyte divided into aerial shoot and rhizome and lacking true roots plant order - the order of plants class Psilopsida, class Psilotatae, Psilopsida, Psilotatae - whisk ferns; comprising the family Psilotaceae or Psilotatae: vascular plants with no roots, partial if any leaf differentiation, and rudimentary spore sacs family Psilotaceae, Psilotaceae - small family of lower ferns having nearly naked stems and minute scalelike leaves |